/**
*      author: Y_Yao
*      created: 2025-03-13 10:18:08
**/

#include<bits/stdc++.h>

#define int LL
using namespace std;
using LL = long long;
const LL LLINF = 9e18;
const int INF = 0x3f3f3f3f;
const int N = 1e5 + 7;
int a[N];
int n,m;

void solve()
{
    cin >> n >> m;
    for(int i = 1;i <= n;i++)
    {
        cin >> a[i];
        a[i] = abs(a[i] - m);
    }
    // for(int i = 1;i <= n;i++)
    // {
    //     cout << a[i] << " ";
    // }
    int ans = a[1];
    for(int i = 1;i <= n;i++)
    {
        ans = __gcd(ans,a[i]);
    }
    cout << ans << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}